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Ion Adsorption at Mineral–Water Interfaces
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Ion Adsorption at Mineral–Water Interfaces

A special issue of Minerals (ISSN 2075-163X). This special issue belongs to the section "Crystallography and Physical Chemistry of Minerals & Nanominerals".

Deadline for manuscript submissions: closed (25 January 2022) | Viewed by 16946

Special Issue Editor

Dr. Frank Heberling

E-Mail Website
Guest Editor
Karlsruhe Institute of Technology, Institute for Nuclear Waste Disposal, PO-Box 3640, 76021 Karlsruhe, Germany
Interests: environmental geochemistry; surface science; adsorption; geochemistry; mineral-water interface structure; surface complexation modelling; recrystallization kinetics; calcite; barite; iron-oxides; clay-minerals

Special Issue Information

Dear Colleagues,

Ion adsorption at mineral–water interfaces has a major influence on ion mobility in porous systems, the charging of mineral surfaces in electrolyte solutions, and the colloidal behavior of mineral particles. Thus, it plays a major role in a multitude of settings. These range from environmental issues to industrial applications and may include mobility or bioavailability of toxic substances or nutrients in natural systems as well as filtration, the rheologic behavior of mineral suspensions, or the wetting behavior of mineral surfaces, just to name a few examples for prominent effects, controlled by ion adsorption at mineral–water interfaces.

For this Special Issue, we encourage submissions of studies investigating ion adsorption phenomena on a wide range of scales and using a wide range of theoretical and experimental methods, from atomistic simulations to continuum scale thermodynamic and kinetic models, and from spectroscopic and microscopic experimental investigations on the molecular scale processes to investigations on large-scale natural or technical systems.

Dr. Frank Heberling
Guest Editor

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Minerals is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2400 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • mineral–water interfaces
  • mineral surface reactions
  • ion adsorption
  • mineralogy
  • geochemistry
  • surface science
  • surface charge
  • ion mobility
  • spectroscopy
  • microscopy
  • atomistic simulations
  • thermodynamic models

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Published Papers (6 papers)

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Research

15 pages, 3977 KiB  
Article
A Kinetic Monte Carlo Approach to Model Barite Dissolution: The Role of Reactive Site Geometry
by Inna Kurganskaya, Nikolay Trofimov and Andreas Luttge
Minerals 2022, 12(5), 639; https://doi.org/10.3390/min12050639 - 18 May 2022
Cited by 9 | Viewed by 2512
Abstract
Barite (Ba[SO4]) is one of the promising candidates for sequestration of radioactive waste. Barite can incorporate radium (Ra) and form ideal solid solutions, i.e., (Ba,Ra)[SO4]. Together with isostructural celestite (Sr[SO4]), ternary solid solutions, (Ba,Sr,Ra)[SO4], may [...] Read more.
Barite (Ba[SO4]) is one of the promising candidates for sequestration of radioactive waste. Barite can incorporate radium (Ra) and form ideal solid solutions, i.e., (Ba,Ra)[SO4]. Together with isostructural celestite (Sr[SO4]), ternary solid solutions, (Ba,Sr,Ra)[SO4], may exist in natural conditions. Our fundamental understanding of the dissolution kinetics of isostructural sulfates is critically important for a better risk assessment of nuclear waste repositories utilizing this mineral for sequestration. So far, the barite-water interface has been studied with experimental methods and atomistic computer simulations. The direct connection between the molecular scale details of the interface structure and experimental observations at the microscopic scale is not yet well understood. Here, we began to investigate this connection by using a kinetic Monte Carlo approach to simulate the barite dissolution process. We constructed a microkinetic model for the dissolution process and identified the reactive sites. Identification of these sites is important for an improved understanding of the dissolution, adsorption, and crystal growth mechanisms at the barite–water interface. We parameterized the molecular detachment rates by using the experimentally observed etch pit morphologies and atomic step velocities. Our parameterization attempts demonstrated that local lattice coordination is not sufficient to differentiate between the kinetically important sites and estimate their detachment rates. We suggest that the water structure and dynamics at identified sites should substantially influence the detachment rates. However, it will require more work to improve the parameterization of the model by means of Molecular Dynamics and ab initio calculations. Full article
(This article belongs to the Special Issue Ion Adsorption at Mineral–Water Interfaces)
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15 pages, 3032 KiB  
Article
Magnesium Coprecipitation with Calcite at Low Supersaturation: Implications for Mg-Enriched Water in Calcareous Soils
by Mostafa Abdollahpour, Frank Heberling, Dieter Schild and Rasoul Rahnemaie
Minerals 2022, 12(2), 265; https://doi.org/10.3390/min12020265 - 19 Feb 2022
Cited by 1 | Viewed by 2610
Abstract
The concentrations of magnesium (Mg) and calcium (Ca) in natural aqueous environments are controlled by sorption and dissolution–precipitation reactions. Ca binding in calcareous soils depends on the degree of solution saturation with respect to CaCO3. Mg may be bound in precipitating [...] Read more.
The concentrations of magnesium (Mg) and calcium (Ca) in natural aqueous environments are controlled by sorption and dissolution–precipitation reactions. Ca binding in calcareous soils depends on the degree of solution saturation with respect to CaCO3. Mg may be bound in precipitating calcite. Here, we investigated Mg incorporation into calcite via the recrystallization of vaterite, which simulates a very low supersaturation in a wide range of Mg to Ca ratios and pH conditions. Increasing the Mg to Ca ratios (0.2 to 10) decreased the partition coefficient of Mg in calcite from 0.03 to 0.005. An approximate thermodynamic mixing parameter (Guggenheim a0 = 3.3 ± 0.2), that is valid for dilute systems was derived from the experiments at the lowest initial Mg to Ca ratio (i.e., 0.2). At elevated Mg to Ca ratios, aragonite was preferentially formed, indicating kinetic controls on Mg partitioning into Mg-calcite. Scanning electron microscopy (SEM-EDX) analyses indicated that Mg is not incorporated into aragonite. The thermodynamic mixing model suggests that at elevated Mg to Ca ratio (i.e., ≥1) Mg-calcite becomes unstable relative to pure aragonite. Finally, our results suggest that the abiotic incorporation of Mg into calcite is only effective for the removal of Mg from aqueous environments like calcareous soil solution, if the initial Mg to Ca ratio is already low. Full article
(This article belongs to the Special Issue Ion Adsorption at Mineral–Water Interfaces)
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12 pages, 982 KiB  
Article
Neptunium and Uranium Interactions with Environmentally and Industrially Relevant Iron Minerals
by Luke T. Townsend, Kurt F. Smith, Ellen H. Winstanley, Katherine Morris, Olwen Stagg, J. Frederick W. Mosselmans, Francis R. Livens, Liam Abrahamsen-Mills, Richard Blackham and Samuel Shaw
Minerals 2022, 12(2), 165; https://doi.org/10.3390/min12020165 - 28 Jan 2022
Cited by 4 | Viewed by 3322
Abstract
Neptunium (237Np) is an important radionuclide in the nuclear fuel cycle in areas such as effluent treatment and the geodisposal of radioactive waste. Due to neptunium’s redox sensitivity and its tendency to adsorb strongly to mineral phases, such as iron oxides/sulfides, [...] Read more.
Neptunium (237Np) is an important radionuclide in the nuclear fuel cycle in areas such as effluent treatment and the geodisposal of radioactive waste. Due to neptunium’s redox sensitivity and its tendency to adsorb strongly to mineral phases, such as iron oxides/sulfides, the environmental mobility of Np can be altered significantly by a wide variety of chemical processes. Here, Np interactions with key iron minerals, ferrihydrite (Fe5O8H·4H2O), goethite (α-FeOOH), and mackinawite (FeS), are investigated using X-ray Absorption Spectroscopy (XAS) in order to explore the mobility of neptunyl(V) (Np(V)O2+) moiety in environmental (radioactive waste disposal) and industrial (effluent treatment plant) scenarios. Analysis of the Np LIII-edge X-ray Absorption Near-Edge Structure (XANES) and Extended X-ray Absorption Fine Structure (EXAFS) showed that upon exposure to goethite and ferrihydrite, Np(V) adsorbed to the surface, likely as an inner-sphere complex. Interestingly, analysis showed that only the first two shells (Oax and Oeq) of the EXAFS could be modelled with a high degree of confidence, and there was no clear indication of Fe or carbonate in the fits. When Np(V)O2+ was added to a mackinawite-containing system, Np(V) was reduced to Np(IV) and formed a nanocrystalline Np(IV)O2 solid. An analogous experiment was also performed with U(VI)O22+, and a similar reduction was observed, with U(VI) being reduced to nanocrystalline uraninite (U(IV)O2). These results highlight that Np(V) may undergo a variety of speciation changes in environmental and engineered systems whilst also highlighting the need for multi-technique approaches to speciation determination for actinyl (for example, Np(V)O2+) species. Full article
(This article belongs to the Special Issue Ion Adsorption at Mineral–Water Interfaces)
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17 pages, 2202 KiB  
Article
In Situ EXAFS Study of Sr Adsorption on TiO2(110) under High Ionic Strength Wastewater Conditions
by Arjen van Veelen, Paul C. M. Francisco, Nicholas P. Edwards, Julian Frederick W. Mosselmans, Tsutomu Sato and Roy A. Wogelius
Minerals 2021, 11(12), 1386; https://doi.org/10.3390/min11121386 - 8 Dec 2021
Cited by 3 | Viewed by 2879
Abstract
In order to provide important details concerning the adsorption reactions of Sr, batch reactions and a set of both ex situ and in situ Grazing Incidence X-ray Absorption Fine Structure (GIXAFS) adsorption experiments were completed on powdered TiO2 and on rutile(110), both [...] Read more.
In order to provide important details concerning the adsorption reactions of Sr, batch reactions and a set of both ex situ and in situ Grazing Incidence X-ray Absorption Fine Structure (GIXAFS) adsorption experiments were completed on powdered TiO2 and on rutile(110), both reacted with either SrCl2 or SrCO3 solutions. TiO2 sorption capacity for strontium (Sr) ranges from 550 ppm (SrCl2 solutions, second order kinetics) to 1400 ppm (SrCO3 solutions, first order kinetics), respectively, and is rapid. Sr adsorption decreased as a function of chloride concentration but significantly increased as carbonate concentrations increased. In the presence of carbonate, the ability of TiO2 to remove Sr from the solution increases by a factor of ~4 due to rapid epitaxial surface precipitation of an SrCO3 thin film, which registers itself on the rutile(110) surface as a strontianite-like phase (d-spacing 2.8 Å). Extended X-ray Absorption Fine Structure (EXAFS) results suggest the initial attachment is via tetradental inner-sphere Sr adsorption. Moreover, adsorbates from concentrated SrCl2 solutions contain carbonate and hydroxyl species, which results in both inner- and outer-sphere adsorbates and explains the reduced Sr adsorption in these systems. These results not only provide new insights into Sr kinetics and adsorption on TiO2 but also provide valuable information concerning potential improvements in effluent water treatment models and are pertinent in developing treatment methods for rutile-coated structural materials within nuclear power plants. Full article
(This article belongs to the Special Issue Ion Adsorption at Mineral–Water Interfaces)
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25 pages, 2334 KiB  
Article
Uranium (VI) Adsorbate Structures on Portlandite [Ca(OH)2] Type Surfaces Determined by Computational Modelling and X-ray Absorption Spectroscopy
by Christopher A. Lee, Arjen van Veelen, Katherine Morris, J. Fred W. Mosselmans, Roy A. Wogelius and Neil A. Burton
Minerals 2021, 11(11), 1241; https://doi.org/10.3390/min11111241 - 8 Nov 2021
Cited by 4 | Viewed by 2563
Abstract
Portlandite [Ca(OH)2] is a potentially dominant solid phase in the high pH fluids expected within the cementitious engineered barriers of Geological Disposal Facilities (GDF). This study combined X-ray Absorption Spectroscopy with computational modelling in order to provide atomic-scale data which improves [...] Read more.
Portlandite [Ca(OH)2] is a potentially dominant solid phase in the high pH fluids expected within the cementitious engineered barriers of Geological Disposal Facilities (GDF). This study combined X-ray Absorption Spectroscopy with computational modelling in order to provide atomic-scale data which improves our understanding of how a critically important radionuclide (U) will be adsorbed onto this phase under conditions relevant to a GDF environment. Such data are fundamental for predicting radionuclide mass transfer. Surface coordination chemistry and speciation of uranium with portlandite [Ca(OH)2] under alkaline groundwater conditions (ca. pH 12) were determined by both in situ and ex situ grazing incidence extended X-ray absorption fine structure analysis (EXAFS) and by computational modelling at the atomic level. Free energies of sorption of aqueous uranyl hydroxides, [UO2(OH)n]2–n (n = 0–5) with the (001), (100) and (203) or (101) surfaces of portlandite are predicted from the potential of mean force using classical molecular umbrella sampling simulation methods and the structural interactions are further explored using fully periodic density functional theory computations. Although uranyl is predicted to only weakly adsorb to the (001) and (100) clean surfaces, there should be significantly stronger interactions with the (203/101) surface or at hydroxyl vacancies, both prevalent under groundwater conditions. The uranyl surface complex is typically found to include four equatorially coordinated hydroxyl ligands, forming an inner-sphere sorbate by direct interaction of a uranyl oxygen with surface calcium ions in both the (001) and (203/101) cases. In contrast, on the (100) surface, uranyl is sorbed with its axis more parallel to the surface plane. The EXAFS data are largely consistent with a surface structural layer or film similar to calcium uranate, but also show distinct uranyl characteristics, with the uranyl ion exhibiting the classic dioxygenyl oxygens at 1.8 Å and between four and five equatorial oxygen atoms at distances between 2.28 and 2.35 Å from the central U absorber. These experimental data are wholly consistent with the adsorbate configuration predicted by the computational models. These findings suggest that, under the strongly alkaline conditions of a cementitious backfill engineered barrier, there would be significant uptake of uranyl by portlandite to inhibit the mobility of U(VI) from the near field of a geological disposal facility. Full article
(This article belongs to the Special Issue Ion Adsorption at Mineral–Water Interfaces)
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17 pages, 3012 KiB  
Article
Adsorption of Polyions on Flat TiO2 Surface
by Tin Klačić, Jozefina Katić, Danijel Namjesnik, Jasmina Jukić, Davor Kovačević and Tajana Begović
Minerals 2021, 11(11), 1164; https://doi.org/10.3390/min11111164 - 21 Oct 2021
Cited by 3 | Viewed by 1750
Abstract
In this study, the surface properties of Ti/TiO2 substrate before and after the adsorption of polyelectrolytes were investigated. As model polyelectrolytes, strongly charged polycation poly(diallyldimethylammonium) (PDADMA) and strongly charged polyanion poly(4-styrenesulfonate) (PSS) were used. Initially, the bare titanium substrate was characterized by [...] Read more.
In this study, the surface properties of Ti/TiO2 substrate before and after the adsorption of polyelectrolytes were investigated. As model polyelectrolytes, strongly charged polycation poly(diallyldimethylammonium) (PDADMA) and strongly charged polyanion poly(4-styrenesulfonate) (PSS) were used. Initially, the bare titanium substrate was characterized by means of ellipsometry, atomic force microscopy (AFM), cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and measurements of inner surface potential using crystal electrode (CrE). It was shown that the substrate surface is very smooth with the roughness of 3.5 nm and oxide layer thickness of 3.8 nm. After the adsorption of PDADMA and PSS, polyelectrolyte-coated titanium surface was examined using the above-mentioned methods under the same conditions. It was found that both PDADMA cations and PSS anions form a stable polymeric nanofilm on Ti/TiO2 surface that partially covers the surface, without significant impact on the surface roughness. The corrosion protection effectiveness values indicate that the corrosion properties were greatly enhanced upon polyion adsorption and polyelectrolyte coating formation on the flat TiO2 surface. The obtained results were additionally confirmed by inner surface potential measurements. According to the methods employed, PDADMA nanofilm modification offers enhanced corrosion protection to the underlying titanium material in sodium chloride electrolyte solution. Full article
(This article belongs to the Special Issue Ion Adsorption at Mineral–Water Interfaces)
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